Gaseous and vapor electric



G. E. INMAN April 28,1942.

GASEOUS AND VAPOR ELECTRIC DISCHARGE DEVICE 2 Sheets-FSheet 1 Original Filed-Sept. l l, 1934' nv entor George'Eln a by His Attorney;

GASEOUS AND VAPOR ELECTRIC DISCHARGE DEVICE I Original Filed Sept. 11, 1934 2 Sheets-Sheet 2 All Inventor: George E. Inman.

His Attorney Reissued Apr. 28, 1942 GASEOUS AND VAPOR ELEc'rmo DISCHARGE DEVICE George E. Inman, East Cleveland, Ohio, assigrior to General Electric Company, a corporation of New York Original No. 2,103,034, dated December 21, 1937,

Serial No. 743,504, September 11, 1934. Application for reissue October 19, 1939, Serial No.

21 Claims.

My invention relates to gaseous or vapor electric discharge devices containing some working substance providing an lonizable atmosphere during operation,-and particularly todischarge devices of the so-called positive column" type, exemplified in gas lamps such as argon or neon lamps, and in metal vapor lamps such as sodium lamps. Very usually, sodium or other metal vapor lamps include in their working substance 9. small amount of easily ionized gas like neon, argon, etc. (whose partial pressure in the lamp is around 1 or 2 to 7 m. m.) to assist in starting the sodium. or other vapor discharge: i. e., the lamp starts as a gas lamp, and as it heats up operates more and more as a sodium vapor lamp. My invention is especially concerned with the starting of positive column devices, and is very useful in reducing or minimizing the starting voltages of such devices, and in starting relatively long tubular devices. The invention facilitates the starting of l devices with discharge gaps so long that they might otherwise require excessive starting voltages, and also allows of improving the economy of operation of such devices after starting. It is especially adaptable and advantageous for low-pressure positive column glow discharge devices having one or more hot or separately heated electron-emissive- "thermionic-electrodes,as distinguished from so-called.cold electrodes, heated only bythe discharge. 1

Heretofore, discharge devices of this character having relatively long discharge gaps have employed electrodes each resistively heated, with a very small voltage drop between its heatingcurrent leads (usually about 2 volts) for the sake of uniform emission from the electrode surface.

Usually, two leads were run through the stem or end of the lamp bulb for each electrode. For starting such devices, a high voltage across the discharge gap between the coacting electrodes had to be relied on, so that it was generally impossible to start them on an ordinary A. C. lighting circuit 'of about to volts. To provide the low potential (2 volt) drop for heating the electrodes, as well as the high voltage for'the discharge between them, special external arrangements were necessary. As, moreover, the voltage'required at starting very much exceeded the subsequent normal operating voltage of the device, voltage-controlling means had to be provided to permit high starting voltage andassure suitably reduced operating voltage.

I have found that by using different electrodes from those heretofore used in such positive column discharge devices, and changing various;

associated features, the starting of such dev-ice's can be facilitated, and a longer lamp started on a given voltage; their starting voltages reduced; their economy in normal operation improved; their construction and accessories simplified and cheapened; and various other advantages secured. Instead of electrodes with only a 2 volt drop between their heating-current leads, I employ one or more electrodes with heating means taking at starting a voltage considerably over 2 volts or the like, and, indeed, in excess of the ionization potential of the atmosphere in the envelope of the device at or during starting. Across the heating-current circuit of this electrode-heating means, I cause or' permit a preliminary, local discharge,-in parallel with said heating means or a part thereof,--thus ionizing enough of the atmosphere in the device to facilitate starting of the main discharge. To minimize or prevent undesirablepersistence of such local discharge,- suitable control over the voltage across the heating circuit is provided, to reduce it sufficiently to mitigate or terminate the local discharge. This does not necessarily require reducing the heating-circuit voltage actually below the ionization potential of the .atmosphere in the device, after the main discharge has'started,

but only reducing it to a point where the local discharge gap is too' great for such reduced heating-circuit voltage to maintain a local discharge of any magnitude.

A, very simple arrangement consists 'of an indirectly heated uni-potential type of electrode j having its electron-emissive portion or surface connected in parallel with a heating'resistance (external or internal) of suitably high value, and

also having a current lead to the resistance (or an associated part) suitably exposed close to the My invention also aims at improving the efii- I ciency of low pressure positive column or cathodic vapor discharge devices characterized by a diffuse glow discharge, that generally appears to fill the whole envelope, as in sodium vapor lamps, by uniformly heating their envelope's,-even in cases when the starting features above set forth are not employed.

Various other features and advantages of my invention will appear from the following description of species thereoi,-and from the drawings.

In the drawings, Fig. 1 is a side view of one form of positive column discharge device embodying my invention} with 'a wiring diagram of its electrical connections.

Fig. 2 shows a'longitudinal or axial mid-section through one of the electrodes shown in'Fig. 1.

Fig. 3 is a similar view of alike device with difierent and somewhat simpler circuit features.

Fig. 4 is a side view of asimpler form of discharge device.

Figs. 5, 6, 7, and 8 are similar views of still other Fig. 1 shows a device well adapted for use as a low pressure positive column glow discharge metal vapor lamp (e. g., a sodium lamp) containing easily ionizable starting gas like neon, argon, or-

the like, and suitable for alternating current. It comprises a fairly long tubular (glass) envelope or bulb In with electrodes II, II in its opposite ends, and a pair of current leads l2, lit to each electrode, both (in the present instance) sealed through the corresponding end walls. The elec-' trodes II, II are shown as of unipotential, indirectly heated, thermionic type, and as externally emissive and extending diametrally of the envelope and parallel with one ano'ther,-although these latter details are broadly unessential. While the details of electrode construction areglikewise broadly unessential, yet for the sake of clearness the electrodes II, II may be briefly described (see Fig. 2) aseach comprising an electron-emissive portion consisting of a metal (nickel) base tube I4 with an external surface'or coating ii of emissive material (like barium oxide); shouldered insulative refractory (lava) I capes primary terminals 21), Ill and taps 22, 22 illustrate plugs I5, iii in the ends of the tube, centrally bored for passage of the current'leads I2, 13; and a finely coiled (tungsten) heating wire or filament l'l welded to the leads and extendinglaxially in the tube M. The tube I4 is shown connected to the lead l2 by -a metal (nickel) strip l8,'so that the emissive portion or surface at l5 has virtually the electrical potential of this lead I! and of the end of the filamentary heating resistance I'I that is connected to said lead l2.

Hence the lead l2 requires no insulation within the envelope Ill. The other lead I3 is freely exposed in the envelope in outside the electrode ll,at least over a limited, area, and preferably where it is near(st) the emissive surface l5,to serve as anode for a local discharge between it and the electrode ll.

- As here shown, the leads I2, '12 serve as the current leads of the main discharge circuit to the gap between the electrodes II, II, and each pair of leads 1!; l3 serve as the leads of a heating circult including the corresponding resistance H.

The leads l2, l2 are shown connected to the secondary terminals 20, 20 of a transformer 2| as a source of discharge current at suitably high voltage for starting, and the leads l3, l3 are shown Cal through the resistance(s) l'i, so that special additional ballast resistance for the purpose is not ordinarily needed.

the provision of high starting voltage for the main discharge, and the fact that the heating circuit voltages combined need not necessarily equal (or even approach) the main discharge circuit voltage in order to produce preliminary local discharges between one or both electrodes ll, Il and the lead or leads I3, l3. Quite obviously, the necessary voltages and the currents in the main discharge and heating circuits might be produced in'a great variety of other ways well known to electrical engineers. The connections also illustrate the fact that the voltages for the heating circuits I2, I! need not be thesame, and that, if desired anionizing starting voltage might be for only one such heating circuit, and only one local preliminary discharge thus produced. In this case, the resistances I1, I I would probably, of course, have to be of unequal values.

In operation, starting cold, the turning on of current causes heating of theelectrodes II, II to electron-emissive temperatures by the currents in their heating circuits l2, l3, I2, I 3. With suitable values of the heating resistances I1, H, the heating circuit voltages at starting readily exceed the ionizing potential of argon (15.7 volts) or neon (21.5 volts), so. that with the electron-emission from the surfaces l5, [5, local discharges readily start across the relatively short gaps between the electrodes II, II as cathodes and their leads I3, I I3 as anodes, thus ionizing gas in the envelope [0. The main discharge between the electrodes H, H then starts easily, owing to the relatively large amount of conductive gas thus provided for it, and the higher voltage betweenthe electrodes l I, ll than across each heating circuit I2, l3. But

. as the main discharge increases and the total currentthrough the leads [2, l2 correspondingly increases, the ballast rea-ctance embodied in the transformer 21 takes a larger proportion of the available voltage. Hence the voltage and the local discharge between each electrode H and lead l3 decreases, until the voltage across each circuit l2, l3 sufliciently approaches (or falls below) the ionization potential of the atmosphere in the envelope 1 0, and the local discharge practically ceases. Ordinarily, this occurs before sodium vapor becomes very noticeable in the luminosity of the discharge, because the discharge must heat up the envelope I0 considerably before enough sodium vaporizes to have any importance in the discharge.

For various reasons, the voltage drop along a heater resistance or filament II should not be allowed to become excessive, during either starting or operation. In the first place, the higher this voltage (above the ionization voltage), the greater the consumption of energy in the relatively ineflicient discharge between electrode II and lead l3. In the second place, a serious discharge or arc along the heater filament l1 itself is to be avoided. As the operating voltage is con- 1 discharges at the electrodes H, II, the lower starting voltage thus permitted reduces the amount of ballast needed.

A-positive column lamp of very simple construction can be made to start on a low voltage,

' in Fig. 5.

ments 25 not only serve as definite starting points,'

the like by interconnecting or merging its electrode-heating circuits, including resistances l1, IT, in series with one another and in parallel with the main discharge gap,'provided, of course the main discharge gap is not so long that the heating resistances would be under excessive voltages at starting when so connected. This series connection of the heating resistances may be eithe outside or inside the lamp envelope l0.

Fig. 3 shows such a simplification, with the externalheating circuit leads l3, l3 of the two electrodes II, II interconnected or merged in one lead Ila. A ballast resistance 24 is in series both with the main discharge gap II, II and with the heating circuit from I2 through I3, I31: and I3 to l2, so as to control thevoltages in both. Obviously, the voltages on the two heating resistances I1, I! are together equal to the'main discharge voltage. The operation of the device is substantially the same as that of Fig. .1 device.

Fig. 4 shows a simplification of the device itself by using an internal (molybdenum) lead |3b extending right along through the main discharge gap between the electrodes II, II, instead of an external lead as in Fig. 3. electrodes ,l I, l l are arranged axially in the ends the complications of Fig. 1, by suitable resistance of or in the lead serially interconnecting the electrode heaters II, II.

In the device of Fig. 7, a coiled wire or filamentary resistance 30 (as of tungsten or molybdenum) is interposed in the lead l3b, preferably at mid-length in the main discharge gap, to take any excess of voltage between the electrodes He, Me as compared with what can safely be taken by the electrode heating resistance'l 1, II. By thus nicely adjusting the voltage drop in the resistances I1, I], their enclosure as in Figs. 1-6 becomes unnecessary in many cases. Accordingly, the electrodes 1 le, I Ie are here shown as of In this lamp, the v of the envelope Ill, and the lead I3b also extends axially of the envelope. Experience has shown that such an arrangement is practically satisfactory when the operating and starting voltages are not excessive according to the criteria above set forth,--i..e., when the electrode gap H-ll is not too long ,and when the surface area of the lead I3b is quite small. The lead l3b may preferably be provided with projecting anodes or starting points 25, 25, formed by short cross pieces of wire (tungsten or molybdenum) welded to the lead, adjacent each electrode l I, as shown Such anode projections or enlargebut also bear the brunt of the local starting discharges. By their limited size they provide sufficient anode areas for the local discharges at starting, while limiting the discharges in volume at starting and afterward.

open-ended hollow type, with their open ends toward one another, and internally emissive. While thedetails of their construction are broadly unessential, each of them is shown as consisting of a (nickel) tube Me internally surfaced or coatedwith electron-emissive material (barium oxide) l5, and having an insulative refractory (lava) plug lie in one end only. To protect the resistance coils l1, l1 and 30 from any possibility of undue stretching out under tension due to the weight of the parts (particularly the electrodes He, He), rigid insulative connections between the leads connected by these coils may be pro vided, each shown as consisting of wires 3|, 3| fused into insulative (glass or alumina) beads 32, and welded to the leads at opposite sides of the coils.

In a sodium or similar metal vapor discharge device, the energy absorbed in the intermediate axial resistance 30 during operation is not wasted,

but, on the contrary, tends to improve the overall efliciency of the device,even when the electrode resistances I1, I] are not proportioned to In order to minimize any persistence of local discharge between an electrode II and the corresponding heating current lead I3 or I31), I prefer to limit or minimize the anode area for such discharge,inasmuch as only a small local discharge current-is required to facilitate starting] For this purpose, all but a small area of the heating current lead wire may be insulatively covered. Accordingly, Fig. 5 shows an insulative tube 25 (of glass, or even of more refractory material like alumina) around all of the lead I3b between the electrodes II, Il-, excepting very short places adjacent the latter, where the lead is exposed for starting, and the points 25-, 25 are attached, if used.

Fig. 6 shows a device like Fig. 5 with two 1 additional intermediate exposed starting points produce local discharges to assist in the starting. This the resistance 30 does by heating the walls of the envelope 10 between the electrodes He, He, andthus vaporizing condensed sodium that otherwise accumulates in this normally cool mid-region of the device-naturally cool because of the extra heat from the electrodes H e, He at the ends of the lamp. This obviates forcing the main discharge by a high operating voltage in order to bring the envelope I 0 generally up to the temperature (250 C. for sodium) corresponding to the vapor pressure of the working substance for maximum eiflciency. But the lower the current density of the glow discharge, on the other hand,

the higher its, luminous efllciency; and th heat from the resistance 30 gives the envelope temperature required for eificiency with a low ourrent density in the main discharge. Obviously,

' the heating resistance 30 need not be concentrated in a short length as shown in Fig. 6, but may be extended or stretched out to cover as much as desired of theinterval between the electrodes He, lle,so as to give as even a temperature as possible between them and throughout the length of the device, and so keep up a higher vapor pressure of sodium in the device. Axially located as shown, the resistance 30 heats the en velope walls evenly all the way around, which is important to assure adequate vapor pressure of sodium for efiicient operation.

In a sodium lamp, red light from a filamentary heating resistance 30 operating at suitable low temperature serves to improve the quality of the'light, which by itself is too predominantly yellow for many purposes.

If the filamentary resistance 30 is heated to incandescence under the relatively high starting voltage and current through it, or if it is coatedwith emissive material (like barium oxide), then it may become electron-emissive during starting, and act as a sort of temporary intermediate auxiliary electrode to assist in starting: i. e.. the local discharges at the electrodes He, He may be followed by intermediate discharges between each of these electrodes and the heating filament 30,

thus ionizing more gas between the main electrodes and thereby further facilitating starting of the main discharge between them. Such action can be prevented, of course, by making the resistance 30 such as not'to reach an incandescent or electron-emissive temperature during charge or arcing along this resistance 30 may nevertheless be obviated by insulatively (and refractorily) enclosing it,-provided, of course, the voltage drop in question is not too high.

Fig. 8 shows a lamp somewhat similar to that of Fig. 7, but having the intermediate resistance 30! extended over the whole interval between the electrodesllf, III and the heating resistances I1f, I1). As shown, these resistances Ill, 30!, I11 are all combined in one length of iinely coiled wire or filament (tungsten or molybdenum), which is greatly stretched out between the electrodes I I II), and left concentrated within them. This afiords the necessary resistances at theelectrodes I If, III to take voltages above the ionization potential of the atmosphre in the device at starting, and thus assure local discharges between each electrode and the adjacent portion (I1f or 30)) of the long filament, to assist in starting. The stretching out of the intermediate resistance 30f over a long length minimizes the likelihood of discharges or arcs along it during operation if the voltage drop on it is rather high. The uniform heating of the envelope IIIf throughout its length by the electrodes and the filamentary resistance 30] improves the efliciency of a sodium vapor or similar glow discharge device, regardless of whether the resistances I1 I1 are proportioned to produce local starting discharges or not.

While the details of construction of the device shown in Fig. 8 are not broadly essential they present features of peculiar novelty and advantage. As here shown, the envelope I) is cylincovering 43, and intermediate anchor supports 44, 44, 44 are fused into this covering 43 and have pigtail' loops on their free ends to embrace the filament f.

. For various reasons, it is desirable to exclude hot sodium vapor or the like from the terminal post structures 31, 31; and for this purpose, a shut-oil disc 48 (preferably suitably refractory or thermo-insulative, as well as electrically insulative) is shown in each post-nipple 36, 36, formingv a septum across the'interior of the nipple.

The current lead 40 or 4| (as the case may be) extends through a hole in thedisc 4B, and this hole and the Joint around the disc edge are sealed tight with suitable insulative cement, which at the lead 4I may also form an insulative joint between the tube 43 and the disc 48. A fine tube 49 extends through the disc 48, to permit the interior of the terminal post 31 to be exhausted through the bulb proper and the tip 38. The opening through the tube 49 is so fine as to be automatically closed or sealed up by sodium or the like condensing in the tube when the device is first operated. Along with their other functions, the shut-oils 48, 48 reduce the loss of heat by transmission via th terminals 31, 31.

In Figs. 3,, 4, 5, 6 '7, and 8, various parts and asbestos. jacket gasket (not shown) to conserve drical, with a hemispherical upper end or bowl.-

rather than more strictly tubular as in Figs. 1-7,-

and isequipped with a unitary base and contact terminal structure 35 of the type commonly known as a bi-post base. This structure 35 comprises a cup-like (glass) body with downward-projecting hollow nipples 36, 36 to which are fused hollow metal terminal posts or-thimblesleeves 31, 31, closed attheir lower ends. The exhaust tip 38 on the glass body 35 is also shown. Metal lead wires 40, 41 are attached to the hollow contact terminals 31, 31 inside the latter, and extend up through the nipples 36, 36 into the cup-like body 35, where the lead 40 is bent to extend radially inward to (and across) the center or axis of the envelope lilfjwhil the lead 4| extends up near the bowl end of the (envelope before being similarly bent. The nickel tube base heat. A compensating resistance, reactor, or

transformer (as witness Fig. 1) may be used to v Letters Patent of the United States, is:

1. A positive column electric discharge device comprising an envelope containing an ionizable gaseous atmosphere therein for the starting and operation ofthe device; widely separated coacting main discharge electrodes in said envelope, one at least thermionic; a. discharge circuit for said main electrodes, and a heating circuit for said thermionic electrode having a relatively short discharge gap thereacross in the atmosphere in said envelope; heating means in said heating circuit for said thermionic main electrode; and voltage-controlling means for said heating circuit automatically permitting thereacross a, voltage sufiiciently exceeding the ionizing potential of the atmosphere in the envelope, during starting,

to produce a local discharge across its said gap and thereby ionize the atmosphere and start the main discharge between said electrodes, and thereafter reducing the heating circuit voltage and thus preventing objectionable persistence of such local discharge.

2. A positive column electric discharge device for operation in conjunction'with voltage-controlling means permitting relatively high starting voltage and assuring reduced operating voltage,

said device comprising an envelope containing an 'the atmosphere in the envelope, during starting,

to produce a local discharge across its said gap and thereby ionize the atmosphere and start the main discharge between said electrodes, and

thereafter taking a reduced voltage preventing objectionable persistence of such local discharge.

3. A positive column electric discharge device for operation in conjunction withvoltage-controlling means permitting relatively high starting voltage and assuring reduced operating voltage, said device comprising an envelope containing an ionizable gaseous atmosphere therein for the starting and operation of the device; widely separated coacting main discharge electrodes in said envelope, one at least thermionic and provided with electrical heating means; and a heating circuit in parallel with the discharge gap between said main electrodes and including said heating means, and having a relatively short discharge gap thereacross in the atmosphere in said envelope, in parallel with said heating means; the electrical resistances of said heating means and of the rest of said heating circuit being so proportioned thatunder the influence of said voltagecontrolling means said heating means takes a voltage sufliciently exceeding the ionization potential of the atmosphere in the envelope, during starting, to produce a local discharge across said short gap and thereby ionize the atmosphere and start the main discharge, and thereafter takes a reduced voltage preventing objectionable persistence of such local discharge.

4. A positive column electric discharge device for operation in conjunction with voltage-controlling means permitting relatively high starting voltage and assuring reduced operating voltage,

said device comprising an envelope containing voltage. and assuring reduced operating voltage, said device comprising an envelope containing an .ionizable gaseous atmosphere therein for the starting and operation of the device; widely separated coacting, thermionic main discharge electrodes in said envelope having electrical heating means; and a heating circuit in parallel with the discharge gap between said main electrodes including said heating means in series with one another and having relatively short discharge gaps in the atmosphere in said envelope, in parallel'with said heating means respectively; the electrical resistances of said heating means being so proportioned to'the total resistance of said heating circuit that under the influence of said voltage-controlling means said heating means take voltages sufficiently exceeding the ionization potential of the atmosphere in the envelope, during starting, to produce local discharges across said short gaps and thereby ionize the atmosphere and start the main discharge, and thereafter take reduced voltages preventing objectionable persistence of such local discharges.

6. A positive column electric discharge device for operation in conjunction with voltage-controlling means permitting relatively high start ing voltage and assuring reduced operatingvoltage, said device comprising an envelope containing an ionizable gaseous atmosphere therein for the starting and operation of the device; widely separated coacting thermionic, unipotential main discharge electrodes in said envelope having an ionizable gaseous atmosphere therein for the starting and operation of the device; widely separated coacting main discharge electrodes in said envelope, one at least thermionic and unipoten- 'under the influence of said voltage-controlling means said heating means takes a voltage sufliciently exceeding the ionization potential of the atmosphere in the envelope, during starting, to produce a local discharge across said short gap and thereby ionize the atmosphere and start the main discharge, and thereafter takes a reduced voltage preventing objectionable persistence of such local discharge.

5. A positive column electric discharge device for operation in conjunction with voltage-controlling means permitting relatively high starting electrical heating means; and a heating circuit in parallel with the discharge gap between said main electrodes serially including said heating means and a current lead along through the discharge gap between the electrodes interconnecting the heating means, and also having parts in such close proximity to the emissive surfaces of said electrodes as to provide relatively short discharge gaps in parallel with said heating means, respectively; the electrical resistances of said heating means being so proportioned to the total resistance of said heating circuit that under the influence of said voltage-controlling means said heating means take voltages sufficiently exceeding the ionization potential of the atmosphere in the envelope during starting, to produce local discharges across said short gaps and thereby ionize the atmosphere and start the main discharge, and thereafter take reducedvoltages preventing objectionable persistence of such local discharges.

7. A positive column electric discharge device for operation in conjunction with voltage-controlling means permitting relatively high starting voltage and assuring reduced operating voltage, said device comprising an envelope containing an ionizable gaseous atmosphere therein for the starting and operation of the device; widely separated, coacting, thermionic, unipotential, main discharge supporting electrodes in said envelope having electrical heating means; and a heating circuit in parallel with the discharge gap between said main electrodes serially including said heating-means and a current lead along through the discharge gap between the electrodes interconnecting the heatingmeans, and also having projecting anodes in such close proximity to the emissive surfaces of said electrodes as to providerelatlvely short discharge gaps in parallel with said heating means, re-

spectively; the electrical resistances of said heating means being so proportioned to the total resistance of said heating circuit that under the 6 L Y influence of said voltage-controlling means said heating means take voltages sufliciently exceeding the ionization potential of the atmosphere in the envelope, during starting, to produce local discharges across said short gaps and thereby ionize the atmosphere and start the main diswidely separated, coacting, thermionic, unipotential, main" discharge supporting electrodes in said envelope having electrical heating means;

tial of the atmosphere in the envelope, during Y voltages. v

and a heating circuit in parallel with the discharge gap between said main electrodes seri ally including said heating means and an insulatively covered current lead along through the discharge gap' between the electrode intercon necting the heating means and also having exposed portions in such. close proximity to the emissive surfaces of said electrodes as to provide 7 relatively short discharge gaps in parallel with said heating means, respectively; the electrical resistances of said heating means being so pro- 3 portioned to the total resistance of said heating circuit that under the influence of said voltagecontrolling means said heating means take voltages sufliciently exceeding the ionization potenstarting, to produce local discharges across said short gaps and thereby ionize the atmosphere and start the main discharge, and thereafter take reduced voltages preventing objectionable persistence of such local discharges.

9. A positive column electric discharge device 'for operationin conjunction with voltage-controlling means permitting'relatively high starting voltage and assuring reduced operating voltage, said device comprising an envelope containing an ionizable gaseous atmosphere therein for the starting and operation of the device;

widely separated, coacting, thermionic, unipotential, main discharge supporting electrodes in said envelope having electrical heating means;

and a heating circuit in parallel withthe discharge gap between said main electrodes serially including said-heating means and'an insulatively covered current leadalong through the discharge gap between the electrodes interconnecting the heating means, and also having exposed anode points in such close proximity to the emissive surfaces or said electrodes as to provide relatively short discharge gaps in parallel with said heating means, respectively, and also at intervals between them; the electrical resistances of said heating means being so proportioned to the total resistance of said heating circuit that under the influence of said voltage-controlling means-said heating means take voltages sufii-" ciently exceeding the ionization potential ofthe atmosphere in the envelope, during starting, to

, produce local discharges across said short gaps and thereby ionize the atmosphere and start the main discharge, and thereafter ,take reduced 10. 1} positive column electricdischarge device for operation in conjunctionwith voltage-controlling means permitting relatively high starting voltage and' assuring reduced operating voltage, 7

said device gomprising an envelope containing an ionizable gaseous atmosphere therein for the starting and operation of the device; widely sepa-' rated, coacting thermionic, unipotential, main discharge supporting electrodes in said envelope having electrical heating means; and a heating circuit in parallel with the discharge gap between said main electrodes serially including said heating means and a currentlead embodying substantial resistance extending along through the discharge gap between the electrodes interconnecting the heating means, and also having parts in such close proximity to the emissive surfaces of said electrodes as to provide relatively short discharge gaps in parallel with said heating means, respectively; said heating means being so proportioned to the total resistance of said' heating circuit that under the influence of said" voltage-controlling means said heating means take voltages sufliciently exceeding the ionization potentialof the atmosphere in the envelope, during starting, to produce local discharges across said short gaps and thereby ionize the atmosphere and start the main discharge, and thereafter take reduced voltages.

11. A positive column electric discharge device said discharge gap, and having coiled end por- 0 ing starting, to produce local discharges across said short gaps and thereby ionize the atmostions for heating the electrodes and a relatively uncoiled intermediate portion, and being in such close proximity to the emissive surfaces of said electrodes as to provide relatively short discharge gaps in parallel with said end portions, respectively; the resistances of said coiled end portions being so proportioned to the total resistance of said heating circuit that under the influence of said vqltage-controlling means said end portions take voltages sufficiently exceeding the ionization potential of the atmosphere in the envelope, durphere and start the main discharge, and thereafter take reduced voltages preventing objectionable persistence' of. such local discharges.

12. An electric discharge lamp comprising an envelope, a charge of vaporizable working substance in said envelope producing only a small vapor pressure therein, with a difl'use electric discharge, during operation of .the lamp; coacting, thermionic, unipotential, electrodes axially arranged in said envelopeand having electricalheating means; and a heating circuit in parallel with the discharge gap between said electrodes serially including the said heating means, with a current lead embodying substantial resistance extending axially of the envelope along through said discharge gap interconnecting said electrodes.

13. An electric discharge lamp comprising an envelope, 2. charge or vaporizable working substance in said envelope producing only a small vapor pressure therein, with a diffuse electric discharge, during operation 01' the lamp; coacting, thermionic, unipotential, electrodes axially arranged in said envelope; and a filamentary heater extending axially of the envelopealong through the discharge gap between'said electrodes, and having coiled end portions for heating the electrodes and a relatively uncoiled intermediate portion for uniformly velope walls all around it.

14. Apositive column gaseous electric discharge device comprising a sealed elongated envelope containing an ionizable gaseous atmosphere, widely separated coacting electrodes in said enve-' lope, at least one of said electrodes being a heatable thermionic electrode so proportioned that the voltage drop thereacross sufliciently exceeds the ionizing potential of the atmosphere in the envelope, during starting, to produce a local discharge thereacross, the length of the gap between said coacting electrodes being materially greater than the length of the path of said local discharge.

15. A gaseous electricdischarge device comprising a sealed envelope containing, an ionizable heating the enatmosphere, widely separated coacting electrodes in said envelope, at leastone of said electrodes being a thermionic electrode soproportioned that.

the voltage drop thereacross is sufficiently high to produce a local discharge, means to supply sumcient electrical energy across said thermionic electrode to first produce the said local discharge, means to supply suflicient electrical energy across the gap between said electrodes to thereafter start the main discharge between said coacting electrodes, and means for effecting cessation of the said local discharge during normal operation or the device.

16. A gaseous electric discharge device comprising a sealed envelope containing an ionizable atmosphere, widely separated coacting electrodes in said envelope, each of said electrodes being a thermionic electrode comprising a resistance so proportioned that the voltage drop'thereacross is sufliciently high to produce a local discharge across parts of the electrode, a discharge circuit for normally maintaining a discharge-across the gap between said electrodes, and a heating circuit including the resistances and automatically permitting suflicient electrical energy to flow through said resistances to produce the local discharges and thereafter efiecti'ng a cessation of the said local discharges during normal operation-of the .device.

1'7. A gaseous electric discharge device comprising a sealed envelope containing an ionizable atmosphere, widely separated coacting electrodes in said envelope, at least one of said electrodes being ,a thermionic electrode comprising a resistance so proportioned that the'voltage drop thereacross is sufliciently high to produce a local discharge across parts of the electrode, means to connectsaid resistance in a heating circuit,

and means to connect said electrodes in an oper: ating circuit, said heating circuit being designed to furnish a sumcient potential across said resaid resistances in a heating circuit in parallel with the discharge gap between said electrodes, and means to connect said electrodes in an operating circuit, said heating circuit being designed to furnish a suillcient potential across said resistances, only during starting of the device, to

produce the said local discharges and thereby asslst in the starting of the main discharge between said electrodes. I

19. A gaseous electric discharge device comprising a sealed envelope containing an ionizable atmosphere, widely separated coacting electrodes in said envelope, each oi! said electrodes being a thermionic electrode comprising a resistance so proportioned that the voltage drop thereacross is sufliciently high to produce a local discharge across parts of the electrode, a ballast impedance, means to connect one end of each 0! the electrode resistances across a source of electrical energy with the said ballast impedance in serieswith the device, and means to connect the otherends of J said resistances together to provide a heating circuit through said resistances in parallel with the discharge gap between said electrodes, the said heating circuit and ballast impedance being designed; to afford a sutllcient flow of electrical energy through said resistances, only during starting of the device, to produce the said local discharges and thereby assist in the starting of the main discharge between said electrodes. 4

i 20. A gaseous electric discharge device com-.- prlsing a sealed envelope containing an ionizable atmosphere, widely separated coacting electrodes in said envelope, each of said electrodes being a thermionic electrode comprising a resistance so proportioned that the voltagedrop thereacross is sufficiently high to produce a local discharge across parts of the electrode, means connecting slstance, only during starting of the device, to

produce the said local discharge ,and thereby assist in the starting of the main discharge between said electrodes.

18. A gaseous electric discharge device I prising a sealed envelope containing anionizable atmosphere, widely separated coacting electrodes in said envelope, each'of said electrodes being a thermionic electrode comprising a resistance so proportioned that the voltage drop thereacross is sufllciently high to produce a local discharge across parts of the electrode, means to connect an end of each of said resistances together in a heating circuit in multiple with the arc gap between said electrodes, and connections for -connecting the opposite ends of said resistances containing an ionizable gaseous atmosphere,

widely separated coacting electrodesin said envelope, each of said electrodes being a thermionic electrode comprising a resistance member so proportioned that the voltage drop thereacross sufllciently exceeds the'ionizing potential oi. the atmosphere in the envelope, during starting, to produce a local discharge thereacross, said electrodes alsd each comprising a conductive member'electrically connected to oneend of the associated resistance member and extending to a point adjacent the opposite end oi. said resistance member to provide a short local arc gap adjacent the said opposite end of the resistance member, the length of the gap between said coacting electrodes being materially greater than the length of the path of said local discharge.

GEORGE a, mum. 

